PROJECT SUMMARY Autoimmune posterior uveitis is an inflammatory eye disease affecting the posterior eye that is difficult to treat and commonly results in vision loss. The overall objective of our work is to improve the clinical outcome for patients with this condition. Posterior uveitis is characterized by a heterogeneous leukocytic infiltrate within the retina and adjacent tissues. Previous research relating to disease pathogenesis has centered on CD4+ T cells and monocytes. Mechanisms involving B cells have received little attention, although new treatments directed against these cells are therapeutic for patients with uveitis. This exploratory project will initiate a new line of research on the role of the B cell in autoimmune posterior uveitis, with initial focus on B cell migration to the retina. The central hypothesis of the proposal is that B cell entry into the retina in autoimmune posterior uveitis is strictly regulated by distinct adhesion molecules on retinal vascular endothelium. A novel murine model of B cell trafficking to the eye is proposed, in which the potent B cell chemokine, CXCL13, will be delivered to the posterior eye by intraocular injection of chemokine-encoding lentivirus. Multiple conditions will be tested to optimize the immunization protocol for maximum influx of B cells. Transgene expression will be monitored by ELISA and immunohistochemistry, and inflammation will be monitored by topical endoscopic fundus imaging and histopathology. Parallel studies of B cell-retinal endothelial interactions will be conducted using human systems, including: a retinal endothelial cell transmigration assay with primary human endothelial cells; and a modified Woodruff-Stamper assay using intact human retina. The role of selected adhesion molecules - intercellular adhesion molecule (ICAM)-1, vascular cell adhesion molecule (VCAM)-1 and activated leukocyte cell adhesion molecule (ALCAM) - in B cell trafficking to retina will be evaluated in the murine model and the human-based assays, using appropriate methods to specifically inhibit adhesion molecule-ligand binding.